How to paint through all mesh during vertex painting?
The only workaround I found is to use the Weights to Vertex Colors addon . It's not a real solution, just a workaround, but since you can paint through the mesh in weight paint mode by unchecking "Limit Selection to Visible" , you can paint there and then convert your weights into vertex colors. But of course it converts it in greyscale (although there's an option to use the rainbow ramp from the weight painting but that's not usable for most textures).

But I think a "Limit to Visible" option in Vertex Paint should definitely be added in Blender.